GridFTP transfer logs obtained from NERSC, SLAC, and NCAR, were analyzed. The goal of the analyses is to characterize these transfers and determine the suitability of dynamic virtual circuit (VC) service for these transfers instead of the currently used IP-routed service. Given VC setup overhead, the first analysis of the GridFTP transfer logs characterizes the duration of sessions. Of the NCAR-NICS sessions analyzed, 56% of sessions would have been long enough to be served with dynamic VC service. An analysis of transfer throughput across four paths, NCAR-NICS, SLAC-BNL, NERSC-ORNL and NERSC-ANL, shows significant variance. An analysis of the potential causes of this variance shows that server-related factors are more important than network-related factors. This is because most of the network links are lightly loaded, which implies that throughput variance is likely to remain unchanged with virtual circuits.